Package FiniteFields

Question

In a Mathematica session, I evaluate:

Needs["FiniteFields`"];
fld = GF[2];

Now, for example, I'd like to compute $a^3+a^5$ for $a \in{Z_2}$. The result I'd like to have is $0$, because in $Z_2$, $a^n=a$ and $a+a=0$.

I tried:

fld[{a^3}] + fld[{a^2}]

But Mathematica gives me:

Subscript[{Mod[a^2 + a^3, 2]}, 2]

How can I simplify $a^3+a^2$ in $Z_2$ to get zero?